1. Field of the Invention
This invention relates generally to an orthodontic appliance, and more particularly to an orthodontic bone anchor that can provide tension usable as fixed pushing, pulling or stabilizing points by the orthodontist in treating the malalignment of the teeth of a patient without disturbing adjacent teeth.
2. Description of Related Art
In traditional tooth movement, orthodontic brackets are placed on the teeth, and the brackets are connected to one another using orthodontic archwires. The orthodontic archwire in conjunction with tension bands guides and provides tooth-moving forces to certain teeth, using other teeth as anchors. This traditional method of tooth movement however, has several potential shortcomings. For example, in some patients, the tooth or teeth to be used as an anchor may be missing. Furthermore, although a particular tooth may be serving as an anchor in resisting an orthodontic force, in reality the tension band on the teeth being moved also will exert a counter-force on this xe2x80x9canchorxe2x80x9d tooth which may cause undesirable movement of the anchor tooth.
Therefore, in treating many orthodontic patients, it is desirable to move some teeth yet stabilize other teeth which otherwise would move due to the reactive forces created in the mouth. Traditionally, this tooth stabilization, or differential tooth movement, has been achieved by applying lower forces in the mouth or by utilizing several teeth as the anchor. However, when lower forces are applied, orthodontic treatment requires significantly more time, and when several teeth are used in combination as an anchor, the resulting tooth-moving response may be somewhat unpredictable.
All orthodontic forces adhere to Newton""s xe2x80x9cLaw of Reciprocal Forces.xe2x80x9d If a tension band force is applied to retract or pull back an object such as a tooth, there exists an xe2x80x9cequal and oppositexe2x80x9d force to move another tooth or object forward. The resistive force value of the teeth is known as anchorage. Orthodontists may offset these reciprocal tendencies by using an extraoral force known as a headgear to augment the resistive force value of the teeth and as a way of obtaining differential tooth movement. Patient compliance is often inadequate as many patients do not want to wear the headgear. Poor compliance compromises orthodontic therapy and often the final result. Orthodontic forces are usually continuous, acting 24 hours a day. Realistically, most patients will not wear headgear more than 10-12 hours/day. Therefore, the posterior anchorage is typically fortified only 40-50% of the time. All too often, inconsistent usage or overt noncompliance will reduce this effect even more.
Endosseous implants which are placed deeply into bone, are useful when physical space within the mouth is available such as through absence of a molar, however, their use is limited in full dentition where space is at a premium. Endosseous implants are also not suitable in juvenile or adolescents because they are inserted into a hole which is drilled into the alveolar (tooth bearing) portion of the jawbone. Insertion of an endosseous implant into these areas will harm unerupted teeth forming in these areas. Since the juvenile and adolescent patients are still growing, an endosseous implant will be engulfed with continuing vertical development of the alveolar bone and will progressively sink to a lower level thereby becoming inaccessible and difficult to remove.
Subperiostal bone anchors have been known and used in dentistry for many years and their value in orthodontics has been acknowledged since at least the mid 1980""s (Turley, J. Dent. Res. 63A:334, 1984). These bone anchors can be attached to bone just about anywhere in the mouth with little, if any likelihood of destruction of bone or teeth. Block and Hoffman first patented (Block, Orthodontic Anchor U.S. Pat. No. 5,066,224; Hoffman, Subperiosteal Bone Anchor; U.S. Pat. No. 5,538,427) then later published (Am. J. Orthod. Dentofac. Orthop. 107:251,1995) an orthodontic anchorage system that did not penetrate the bone as endosteal implants do but merely rested on the surface of the bone.
One of the difficulties with some of the prior art is that the devices were rigid, thick and are not moldable to the unique bone morphology found at the surgical site or into a desired direction. Further, the bone-anchor interface surface was often times very complex, being shaped to allow and foster bone ingrowth. After the many weeks for the prior art to osseointegrate, a further surgical procedure is necessary to uncover a portion of the anchor and attach an extruding abutment.
It will therefore be understood that the prior devices are rigid, cannot be adapted to irregular bony contours at the time of surgery, are somewhat bulky and thus limit intraoral placement to locations where overlying soft tissue is relatively thick, such as in the palate, and require two separate surgical procedures. Additionally the attachment procedure connecting the device to teeth is complex and often requires additional laboratory steps.
In the last 10 years small bone plates in numerous configurations have come into high use in orthognathic and maxillofacial reconstructive surgery with such plates being deformable and contourable to fit to a variety of irregular bony surgical sites. Contourable bone plates of xe2x80x9cYxe2x80x9d, xe2x80x9cTxe2x80x9d, xe2x80x9cLxe2x80x9d and xe2x80x9cIxe2x80x9d shape configurations, and of more complex geometrical shapes, are available in a variety of thicknesses and with a selection of degrees of malleability.
U.S. Pat. No. 5,853,291 to Vincenzo discloses a thin, subperiosteal bone anchor for use in conjunction with orthodontic appliances having a plurality of moldable, scalloped leaves and arms to facilitate bone overgrowth and an upwardly extending stem with a variety of attachment connection mechanisms. The entire base and leaves of the anchor are scalloped to foster osteointegration. A sphere or rectangular tube projects upward. This anchor, although small, thin and moldable to bone, is highly three dimensional with its orthodontic attachment rising up from its planar fixation against the bone, is structured with tapering, leaf-like projections to foster osteointegration, whereas the present invention is in substantially a planar configuration when in use, is designed to be temporary and without osteointegration, includes a tension band holder and wire guide integrally fixated thereon which are structured to receive and attach other orthodontic adjustment and attachment devices and requires less traumatic surgical procedures to remove, thus has less morbidity to the patient.
The plates readily usable in orthognathic and maxillo-facial surgery, as described above, are generally relatively small (about 20-40 mm. in their major dimension). These small, malleable bone plates, often made of a titanium alloy contain a plurality of holes situated over the surface through which standard bone screws and fasteners can pass to attach the plate to bone and through which archwire can be threaded when attaching the distal end of the plate stemarm to orthodontic appliances within the mouth of the patient. Although the small, moldable bone plates function as adequate anchors and do not osteointegrate, the stemarm portion with only holes for attachment to other orthodontic hardware in the patient""s mouth provide limited directional torque and control thereby restricting treatment options, compromising outcome, and often prolonging treatment time. These miniature prior art bone plates can be obtained from a variety of suppliers, e.g. KLS Martin, L. P. of Jacksonville, Fla., see pages 7-9, 35-37, 48, 58-60, 74-77, 101, and 102 of their Surgical Instrument Catalog, 1st edition, for examples and from W. Lorenz of Jacksonville, Fla., see pages 4, 5, 7, 10, 12, 17, 19, 20, 29, and 30 of the 1988 Surgical Instrument Catalog for examples.
In the orthodontic field a need exists for a non-osteointegrating, bendable temporary bone anchor and tension band connector for resisting tension band forces of the tension band attached to a tooth to be moved that includes enhanced directional tension band torque and control, which is installed and removed with minimal surgical trauma, morbidity and healing time. Other teeth not to be moved are not used as anchors.
More particularly, the system includes a flat, rigid body referred to hereinafter as an anchor plate, having a base and one or more arms and at least one aperture through which a screw is positioned to affix the bone plate to the cortical surface of bone attachable at various oral locations, e.g. buccal, labial, lingual and palatal surfaces of the maxillary jawbone and the buccal, labial and lingual surfaces of the mandibular jawbone. An orthodontic tension band bracket, having up to four prongs, is integrally fixated to the rigid body opposite the body arm. The tension band bracket protrudes substantially vertically from the gum substantially parallel to the tooth line but not on an occlusal surface. The arm of the rigid body is surgically fastened to the bone, preferably with bones screws and in 5-7 days when the soft tissue incision has healed, the tension band bracket on the distal end of the rigid body is then attached by a tension band to at least one other orthodontic tension bracket within the patient""s mouth. A guide wire passage can also be affixed to the anchor body. The tension band bracket on the rigid anchor body not only provides multi-directional tension attachment options, but also multi-directional torque based on physical placement in the mouth and selection of the type of tension or guide integrally connected thereto. The guide tube may be connected by rectangular or cylindrical wire. Using the tension band prongs, the anchor body can accommodate elastic bands or thread, chains, springs or by any other suitable type of releasable tension force mechanism or device commonly used in orthodontics. The anchor plate body can also be utilized as anchorage in the space of a missing tooth. It is preferred that the anchor body arm and tension band bracket wire and guide tube be unitarily formed as a single component, but could be separately fixated together as well using different manufacturing compositions so long as the final device is biocompatible and durable.
The rigid anchor body should be thin to lay under the soft tissue against the bone without being bulky and should not osteointegrate. The system serves as an anchor in the mouth usable without prolonged healing and recuperative time after surgical installation and removal and without significant morbidity to the patient. The anchor body is manually moldable to conform to individual bone curvature and into areas difficult to reach. The system is particularly useful where there has been a loss of posterior teeth and thus posterior anchorage and can be used in substantially all patient populations. Because of the increased torque and control and the ability to move teeth in virtually all directions, overall treatment time is reduced.
It is an object of this invention to provide a tension band anchor and wire guide for moving one or more teeth under tension, avoiding the use of other teeth as anchors when movement of such other teeth during treatment is undesirable.
In accordance with these and other objects which will become apparent hereinafter, the instant invention will now be described with particular reference to the accompanying drawings.